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Object Overview
After the invention of the barometer and its establishment as a device grounded in scientific principles, the interest in more accurate weather forecasting steadily grew. By the mid-19th century, the demand for specialized instruments capable of predicting weather conditions based on pressure, wind, and temperature data became pressing. One of the earliest of such devices was the so-called predictive scales, used to generate concise and convenient forecasts. Initially, these were simple rectangular cards made of thick cardboard with rotating disks. Over time, more advanced models appeared: metal or celluloid circles with rotating dials fastened together.
Celluloid, discovered in 1855 by British metallurgist Alexander Parkes, became the first commercially successful plastic. It was light, flexible, and easy to mold, which made it a popular material for manufacturing a wide range of products—from combs and buttons to film and toys. However, celluloid's high flammability later led to its reduced usage.
Weather predictors made from celluloid or metal allowed users to log the current atmospheric pressure, its tendency to change, and the wind direction. By rotating the disks along the scales, the user would input these data as initial parameters and receive a textual forecast like this:
Pat.No 6276/15
celluloid, steel
Predictive scales gained popularity among a wide range of users: from enthusiasts who monitored the weather as a hobby to farmers and sailors. One company that achieved significant success in producing such devices was the British firm Negretti & Zambra. Founded in 1850 by Henry Negretti and Joseph Zambra, the company specialized in the production of scientific and optical instruments. They became widely known for their high-quality barometers, thermometers, and astronomical and meteorological devices. Negretti & Zambra produced instruments for Her Majesty Queen Victoria, Prince Albert, and King Edward VII. Their products were in demand both in scientific circles and among everyday consumers due to the precision and reliability of these instruments.
In 1938, after Ernest Heath conducted 5,295 observations, it was determined that the accuracy of the forecasts had reached 90%. This meant that out of all the observations, only 15 forecasts were incorrect, and 495 were partially correct. These achievements solidified the company's reputation as a manufacturer of reliable and accurate meteorological instruments.
The Celluloid Weather Forecaster presented here, dating from 1920, is made of three celluloid disks fastened together. To obtain a forecast, the user rotates the disks relative to each other, entering data on wind direction, atmospheric pressure in inches of mercury, and the trend of pressure rising or falling. All forecast options are neatly arranged on the back of the forecaster.